Homeless youth constitute a group of adolescents at high risk for substance use disorders and associated psychosocial consequences, yet few interventions have been developed for this population. In response to PA-99-107, NIDA Behavioral Therapies Development Program, this application seeks support for a Stage I developmental project. The four-year research program will develop and test a brief motivational enhancement and service-linking intervention tailored to the special needs of homeless youth. Social structures that have strong influence on adolescent behavior (such as families and schools) are not typically available for intervention. Most youth are not seeking substance abuse treatment. Youth also suffer from high rates of trauma, psychiatric co-morbidity, poverty, and victimization. The intervention will be guided by the Transtheoretical Model of behavior change (Prochaska and DiClemente, 1983). We propose to develop a brief, motivational and service linking intervention aimed at facilitating contemplation of change and use of available services. The intervention will be conducted over several individual meetings over a period of one month. Counselors will provide personalized feedback on substance use behavior and social network relations, use non-confrontational clinical interviewing techniques (Motivational Interviewing), and provide vouchers to encourage participation. The intervention is proposed to be conducted with youth who are not seeking treatment, and to be conducted and integrated with additional services within a local agency. The goals of the intervention will be to encourage homeless adolescents to question social influences about substance use, question assumptions about drug effects, consider treatment for drug problems, and make use of available social services. An initial period of funding will be used to develop a pilot intervention drawing from brief interventions tested with adults and adolescents, and to complete process analyses of service utilization among homeless adolescents. Subsequently, a randomized controlled trial will be conducted. A sample of 100 youth-stratified by age and gender, will be randomly assigned to Motivational Enhancement treatment (ME) or Treatment as Usual (TAU). TAU includes drop-in programs (hygiene, food, material assistance, and case management). Follow-up interviews at one- and three-months post-treatment, will assess substance use, stage of change, and service utilization.